The purpose of the CONFERS Lexicon Working Group (CLWG) is to discuss and refine the terms and language used by CONFERS in the discussion of rendezvous and proximity operations (RPO) and on-orbit servicing (OOS) missions.  The CLWG meets monthly to discuss updates and additions to the CONFERS lexicon.  Attachment A contains the list of terms under consideration in the CLWG.  The CLWG aims to provide consistency within CONFERS and other international organizations of RPO OOS terminology.  Terms in the lexicon generally have dictionary definitions, but in addition have more specialized usage in the context of on-orbit servicing and appear in this lexicon to clarify that specialized usage. As such, the CLWG presents the defined OOS / RPO terminology for CONFERS below:

Lexicon Terms & Definitions – Released April 2022

An action which stops an on-board process and, if necessary, initiates an alternate process to put the servicer spacecraft and client space object in a safe and collision-free state.

An agreed-upon three-dimensional space centered on the passive vehicle (Client Space Object or Servicing Vehicle) in which unintentional contact is possible within the passive anomaly recovery time and ranging and active relative orbit control is needed for safety. Synonym for Proximity Operations Control Volume

The act of effecting a rigid connection between a Servicing Spacecraft and a Client Space Object with the aid of a robotic arm.

The act of establishing a physical connection between two space objects.

An entity/organization procuring the service.

The space object being serviced by the servicer spacecraft.

An operation executed by a space object relative to another space object to avoid contact for a specified amount of time.

A combined client space object and servicer spacecraft after Docking or Berthing.

An on-orbit service in which the servicer spacecraft maintains attitude stability for the combined stack.

On-orbit services enabling increased duration of client operations as a Combined Stack.

When a servicing spacecraft executes a controlled trajectory to effect a rigid connection with a Client Space Object.

Sensing of a Client Space Object by a servicer spacecraft.

A minimum 3-D volume of space around the client space object defined based on navigational uncertainty of each Rendezvous, Proximity Operations and Docking phase or any additional operational volume into which a servicer spacecraft may not enter without approval.

On-orbit activities to physically attach objects to each other.

Activities by a servicer spacecraft or servicing agent on a client space object which require rendezvous and/or proximity operations.

Configured with navigation fiducials and/or grapple/capture interfaces and/or servicing interfaces.

Orbital maneuvers performed between a servicer spacecraft and a client space object on a relative planned path within a pre-defined Approach Volume.

Synonym for Approach Volume.

Changing the orbit of the Client Space Object by a Servicing Vehicle.

Process wherein two space objects (artificial or natural body) are intentionally brought close together through a series of orbital maneuvers at a planned time and place.

An entity/organization that provides On-Orbit Servicing operations.

Spacecraft performing the servicing action.

Action provided by Servicer Spacecraft to the Client Space Object, including but not limited to: inspection, capture, docking, berthing, relocation, refueling, life extension, removal, combined stack control, repair, upgrade, assembly, manufacturing, un-docking, un-berthing, release.

Terms Under Consideration

68 terms are under consideration by the CLWG for inclusion in the CONFERS Lexicon. They are:

  • Abort-Passive
  • Attitude Control Services
  • Augment
  • Automated
  • Autonomous
  • Co-Elliptical
  • Controlled
  • Cooperative Client
  • Co-Orbital
  • Credible Anomaly
  • Credible Failure
  • Departure
  • Drifting Natural Motion Circumnavigation
  • Dynamic Station Keeping (DSK)
  • Fail Operation
  • Fail Safe
  • Fiducial
  • Forced Motion Circumnavigation (FMC)
  • Free Drift
  • Foreign Object Debris (FOD)
  • Grapple
  • Grapple Feature
  • Grappling (verb)
  • Hold
  • Joint Mission Operations
  • Legacy Spacecraft
  • Mating Operations
  • Natural Motion Circumnavigation (NMC)
  • Navigation Data – Absolute
  • Navigation Data-Relative
  • Nominal Mission
  • Non-Contact Support
  • On-orbit Upgrade
  • Orbit Maintenance (Assistance)
  • Passively Safe
  • Passive Anomaly Recovery Time
  • Phases-Launch and Insertion
  • Phases-Rendezvous
  • Phases-Transfer
  • Radial/In-Track/Cross-Track Coordinate Frame
  • Refill
  • Refuel
  • Refueling Value
  • Relative Motion Coordinate Frame
  • Release
  • Removal
  • Rendezvous-Close Approach
  • Rendezvous-Far
  • Repair
  • Replace
  • Resident Space Object (RSO)
  • Resume
  • Retreat
  • Safe Orbit
  • Safety Zone
  • Secondary State Determination
  • Separation
  • Servicing Agent
  • Servicing Operation Termination (SOT)
  • Servicing Operations Initiation
  • Situational Awareness Data
  • Spacecraft Fiducial
  • Synchronized Time
  • Teleoperation
  • Towing
  • Un-Prepared
  • Upgrade
  • Waypoint